Counterbore pilot



April 5, 1966 s. w. JARDINE COUNTERBORE PILOT Filed April 19, 1965 FIGSl NVENTOR United States Patent 3,244,033 COUNTEREGRE PILOT George W.Jardine, 12 Lake Road, Walthsrn, Mass. Filed Apr. 19, 1965, Ser. No.449,011 Claims. (Cl. 7758) The present invention is acontinuation-in-part of application Ser. No. 273,160 filed April 15,1963 and now abandoned.

This invention relates to boring holes in steel, aluminum and othermetal bodies and, more particularly, the invention is concerned with animproved counterbore pilot for counterboring of the class in which acounterbore tool with a centering pilot is caused to pass all the way ora part of the way through a metal body having a previously formed pilothole therein, whereby a thin disc or slug section is formed just beforecompletion of the counterboring operation when boring all the waythrough the material.

In machine operations of this class where holes are continuouslycounterbored in successive workpieces, difficulty arises in connectionwith handling the discs or slug sections which are formed around thecounterbore pilot at the end of each counterboring operation, especiallywhen counterboring thin materials. These slug sections are of annularshape and tend to jam on the counterbore pilot. The jamming action isbrought about, to a large extent, by the pressure of counterboring whichmay tend to force portions of relieved material against the pilot and,in some cases, pressure may cause material to roll over onto the pilot.As a result of these conditions, the slug section does not drop off thepilot readily and much production time is lost by the machine operationin dislodging the slug section from the pilot. In some cases it may evenbe necessary to stop the machine before the slug section can be removed.

I have discovered that this difiiculty can be completely eliminated byreaming the pilot hole in the slug section during the last part of thecounterboring operation so that it is made slightly larger than itsoriginal size in diameter and hence the slug is free to drop off thepilot without interference.

As one suitable means of accomplishing this reaming operation, I havedevised a counterbore pilot member with center cutting means which islocated at the base of the pilot and which functions as an inner reamermember for removing small portions of the slug section immediatelysurrounding the pilot.

By means of this arrangement, I am enabled to increase the size of thepilot :hole in the slug section and jamming or sticking of the slugsection on the pilot is overcome. Thus the slug section readily dropsoff from the pilot. It is also found that by enlarging the pilot hole inthe slug section there is prevented any tendency for material to becomerolled over onto the pilot in an undesirable manner.

The nature of the invention and its other objects and novel featureswill be more fully understood and appreciated from the followingdescription of a preferred embodiment of the invention selected forpurposes of illustration and shown in the accompanying drawings, inwhich:

FIGURE 1 is a view illustrating in cross section a W011ipiece in which acounterbore tool is shown in elevation with the improved counterborepilot of the invention engaged in a counterboring operation;

FIGURE 2 is an end elevational view of a counterbore tool andcounterbore pilot with cutters wherein the circumference of acounterbored hole is indicated at d;

FIGURE 3 is a detail elevational view of an improved 3,244,633 PatentedApr. 5, 1966 counterbore pilot member formed with slug reaming means ofthe invention;

FIGURE 4 is a cross section taken on the line 44 of FIGURE 3;

FIGURE 5 is a detail cross sectional view of a slug section resultingfrom a cut completed by an operation such as that shown in FIGURE 1; and

FIGURE 6 is a plan view of a slug section.

Referring more in detail to the drawings, FIGURE 1 illustratesdiagrammatically the operation of slug reaming by the improved pilot ofthe invention in combination with a counterbore tool being turnedthrough a metal body M in which a pilot hole of a desired diameter hasalready been formed. This illustration does not necessarily representany particular style or make of counterbore tool. Any standard make toolof this class, including the spiral groove and the angled cutter typemay be used with this improved pilot.

The counterbore tool comprises a shank portion 2 on which is supported acutter head 4 having a plurality of cutting edges 6, 8 and 10 or moreaccording to the style or size of counterbore used. It will beunderstood that the shank portion 2 is engaged in a chuck or other wellknown holding device forming part of a drill press or other powerdriving member. As is customary with counterbore tools of the classindicated, I provide in a centrally located bore 12 in the cutter head4, a pilot element 16.

The pilot element or shank portion 16 consists of a reduced cylindricalend which is adapted to fit snugly in the bore 12 and which is formedwith a flat surface 18 designed to prevent turning of the pilot in thecounterbore tool as is customary with other types of pilots. At itsouter end, the pilot or guide portion 20 is formed to a cylindricalshape and may be the same size as the shank portion or enlarged as shownin the drawing which part is chosen of a diameter corresponding to thediameter of the pilot hole in the metal workpiece M already formed. Thisimproved pilot is interchangeable as is customary with other pilots.

In accordance with one preferred embodiment of the invention, I provideon the cylindrical pilot 20 at a point immediately adjacent to therelief groove 14, reamer means 22 which may, for example, consist of aconically tapered body portion formed as an integral part of the pilotand having a plurality of cutting edges as 24, 26 and 28 or more ifneeded to equal the number of cutting edges on the particular make orsize of the counterbore tool used. The pilot cutting edges are of a sizesuch that when the guide portion 20 is fully seated against the cutterhead 4, they will project forwardly a short distance beyond the cuttingedges 6, 8 and 10 of the cutter head 4.

The projecting relationship of cutting edges 24, 26 and 28 is moreclearly illustrated in FIGURE 1 wherein it will be observed that thecutting edges noted are shown projected through the bottom surface ofthe slug section S of the metal body M at 38 while the extreme outermostportions of the cutting edges 6, 8 and 10 are just beginning to cutthrough the bottom of the metal body M. The cutting edges 24, 26 and 28may also, in a preferred form, extend outwardly in an angularly disposedmanner such that a slug remaining will result in a conically shapedhole.

In carrying out the counterboring operation of the invention, the toolis engaged by inserting the guide portion 20 in the pilot hole alreadyformed in the workpiece M. Thereafter, the counterbore tool 4, throughits cutting edges 6, 8 and 10 removes material to form a new hole of theoverall diameter of the cutter 4 and during this period, the conicalreamer 22 follows the pilot all the way through the material andenlarges the pilot hole in the slug section when the material iscounterbored all the way through.

As the pilot starts to pass completely through the material, there isformed a slug section S, which is of annular shape as better shown inFIGURE 6, and which is of a tapering thickness extending radiallyoutward from its center portion. As the pilot goes through the member Mthe reamer member 22 starts to cut portions of the slug section Simmediately surrounding the pilot, and the original pilot hole in theslug section is slightly enlarged as at 30 (FIGURES '5 and 6). As notedtherein the opening 30 has a conical shaped surface 32.

It is pointed out that as the pilot passes through the slug section, theconical reamer 22 tends to keep the tool on centerfor the last smallfraction of the boring operation until the slug section 'has actuallybeen cut away from the member M by'the cutting edges 6, 8 and it).Thereafter, the enlarged conical opening allows the slug to readily dropoff from over the end of the pilot tip 2i) and the tool is "ready forthe next counterboring operation.

'For counterboring part way through the material or spot facing a partsize reamer on the pilot would prevent the formation of a burr at thebottom of the counterbored hole.

As noted above, the reamer means 22, may be con structed as an integralpart of the pilot, especially on small to medium size pilots and mayconsist of angled collars which result in the formation'of a conicallyshaped hole. However, it should be understood that the reamer me'ans'22is intended to be illustrative of various other arrangements, forexample, an arrangement where the pilot cutters may be separately formedand fitted onto the pilot in any suitable manner or onto a shell pilot,collar or disc with cutter-tips overlapping the counterbore cutters oronto the counterbore tool in some desired manner.

While I have shown preferred forms of the invention, it will beunderstoodthat various other modifications may be resorted to in keepingwith the spirit of the appended claims.

I claim:

1. For counterboring a sheet metal workpiece in which a pilot hole ofdesired diameter has already been fon'ned, a counterbore tool comprisinga shank portion adapted to be received in a tool holding device,'acutter head supported on the shank portion, a plurality of cutting edgesprovided on said cutter head for removing material in said counterboringof'said sheet metal workpiece, said edges projecting radially of saidcutter head and defining therebetween a series of passages through whichthe material removed by said counterboring passes all the way throughthe cutter head, said cutter head formed with an axial recess definingtherein a centrally located bore, a pilot for said tool, the pilothaving at its rearward end a shank portion, said shank portion removablyreceived in said bore whereby said pilot is interchangeably mounted onsaid tool, said bore and shank portion locked against relative rotation,a cylindrical guide portion formed at the forward end of said pilot,said forward guide portion having a smooth, non-boring surface andproportioned for a piloting fit in the pilot hole already formed in thesheet metal workpiece whereby it will guide and center said tool in saidhole continuing until said counterboring is almost done, and reamermeans formed on the rearward end of said pilot guide portion proximatesaid cutter head, said reamer means presenting cutting edges extendingoutwardly of said cylindrically guide portion to a diameter greater thanthat of'the tool shank portion and extending outwardly also of theinnermost portion of said cutting edges for reaming, from the protrudingslug section formed around said pilot guide portion upon the completionof said counterboring, small portions of said slug section whichimmediately surround the pilot, whereby to increase the size of thepilot hole in the protruding slug section, to overcome jamming orsticking of the slug section on the pilot, and to enable the slugsection readily to drop off from the pilot.

2. For counterboring a sheet metal workpiece in which a pilot hole ofdesired diameter has already been formed, a counterbore tool comprisinga shank portion adapted to be received in a tool holding device, acutter head supported on the shank portion, a plurality of cutting edgesprovided on said cutter head for removing material in said counterboringof said sheet metal workpiece, said edges projecting radially of saidcutter head and defining therebetween a series of passages through whichthe material removed by said counterboring passes all the way throughthe cutter head, said cutter head formed with an axial recess definingtherein a centrally located bore, a pilot for said tool, the pilothavingat its rearward end a shank portion, said shank portion removablyreceived in said bore whereby said pilot is interchangeably mounted onsaid tool, said bore and shank portion locked against relative rotation,a cylindrical guide portion formed at the forward end of said pilot,said forward guide portion having a smooth, non-boring surface andproportioned for a piloting fit in the pilot hole already formedin-the'sheet metal workpiece whereby it will guide and center said toolin said hole continuing until said counterboring is almost done, and areamer member provided at't'he rear'of-said forward guide portion andadjacent to said cutter head, said reamer member presenting cuttingedges extending outwardly of said cylindrical guide portion to adiameter greater than that of the tool shank portion and extendingoutwardly also of the innermost portion of said cutting edges forreaming, from the protruding slug section formed around said pilot guideportion upon the completion of said counterboring, smallportions of saidslug section which immediately surround the pilot, whereby to increasethe size of the pilot hole in the protruding slug section, to overcomejamming or sticking of the slug section on the'pilot, and to enable theslug section readily'to drop off from the pilot, and said reamer membercutting edgesextending outwardly in an angularly disposed manner so asby their reaming to produce a conically-shaped hole, whereby to keep thetool on center during the last fraction of the counterboring operationuntil the slug section has actually been cut away from the sheet 'metalWorkpiece.

3. In a tool for counterboring a sheet metal workpiece in which thepilot hole of desired diameter has already been formed, the improvementwhich comprises, in combination with a tool shank portion adapted to bereceived in a tool holding device, a cutter head supported on the shankportion, a plurality of cutting edges, provided on said'cutter head forremoving material in said counterboring from said sheet metal workpiece,said edges proiecting radially of said cutter head and definingtherebetween a series of passages through which the material removed bysaid counterboring passes all'the way through the cutter head, saidcutter head formed with an axial recess defining therein a centrallylocated bore, a pilot for said tool, the pilot having at its rearwardend a shank portion, said shank portion removably received insaid borewhereby said pilot is interchangeably mounted on said tool, said boreand shank having means engaging to prevent their relative rotation, acylindrical guide portion formed at the forward end of said pilot, saidforward guide portion having a smooth, non-boring surface andproportioned for a piloting fit in the pilot hole already formed in thesheet metal workpiece whereby it will guide and center said tool in saidhole continuing until said counterboring is almost done, and a reamermember formed on said forward guide portion, said reamer membercomprising a series of center cutting means formed on the rearwardmostportion of the cylindrical surface of said guide portion and proximatesaid cutter head cutting edges, said reamer member cutting meansextending outwardly from and to overlie at least the innermost portionsof said cutter head cutting edges and being angularly dis-r posedrelative to said edges such that chips cut by said reamer member willreadily clear said cutting edges.

4. For counterboring a sheet metal workpiece in which a pilot hole ofdesired diameter has already been formed, a counterbore tool comprisinga shank portion adapted to be received in a tool holding device, acutter head supported on the shank portion, a plurality of cutting edgesprovided on said cutter head for removing material in said counterboringof said sheet metal workpiece, said edges projecting radially of saidcutter head and defining therebetween a series of passages through whichthe material removed by said counterbon'ng passes all the way throughthe cutter head, said cutter head formed with an axial recess definingtherein a centrally located bore, a pilot for said tool, the pilothaving at its rearward end a shank portion, said shank portion removablyreceived in said bore whereby said pilot is interchangeably mounted onsaid tool, said bore and shank portion locked against relative rotation,a cylindrical guide portion formed at the forward end of said pilot,said forward guide portion having a smooth, non-boring surface and beingformed to a diameter corresponding to the diameter of the pilot holealready formed in the sheet metal workpiece and which is substantiallythe diameter at least of said rearward shank portion, a reamer memberprovided on said forward guide portion adjacent to said cutter head,said reamer member comprising a plurality of cutting elements projectingoutwardly of the relatively reduced cylindrical surface of said forwardguide portion and spaced by flutedefining portions of said reducedsurface extending therebetween, said cutting elements reducing graduallyangularly to said surface for clearance and shaped at their radial facesto present cutting edges flaring rearwardly outwardly from said surfaceand defining an acute angle, said flaring edges of said cutting elementsfunctioning to remove from the slug section formed around said pilotguide portion in said counterboring, small portions of said slug sectionwhich immediately surround the pilot, whereby to slightly enlarge theoriginal pilot hole in said workpiece and with a conical-shaped surface,to overcome jamming or sticking of the metal workpiece on the pilot, andto enable the slug section received on the pilot guide portion in saidcounterboring readily to drop off from said pilot.

5. In a tool for counterboring a sheet metal workpiece in which a pilothole of desired diameter has already been formed, the improvement whichcomprises, in combination with a tool shank portion adapted to bereceived in a tool holding device, a cutter head supported on the shankportion, a plurality of cutting edges provided on said cutter head forremoving material in said counterboring from said sheet metal workpiece,said edges projecting radially of said cutter head and definingtherebetween a series of passages through which the material removed bysaid counterboring passes all the way through the cutter head, saidcutter head formed with an axial recess defining therein a centrallylocated bore, a pilot for said tool, the pilot having at its rearwardend a shank portion, said shank portion removably received in said borewhereby said pilot is interchangeably mounted on said tool, said boreand shank having means engaging to prevent their relative rotation, acylindrical guide portion formed at the forward end of said pilot, saidforward guide portion having a smooth, non-boring surface andproportioned for a piloting fit in the pilot hole already formed in thesheet metal workpiece whereby it will guide and center said tool in saidhole continuing until said counterboring is almost done, different sizesof said pilot guide portion being mountable with said pilot shankportion whereby said pilot is interchangeable, and a reamer memberformed on said pilot guide portion, said reamer comprising a series ofcenter cutting means formed rearwardly around the cylindrical surface ofsaid guide portion proximate said cutter head cutting edges, said centercutting means defining therebetween a series of passages through whichchips of material cut by said means pass through the reamer member tosaid cutter head.

References Cited by the Examiner UNITED STATES PATENTS 2,230,645 2/1941Jones l451l6 2,826,104 3/ 1958 Morin 7766 FOREIGN PATENTS 551,811 4/1923France. 203,866 9/1923 Great Britain.

WILLIAM W. DYER, JR, Primary Examiner.

G. A. DOST, Assistant Examiner.

1. FOR COUNTERBORING A SHEET METAL WORKPIECE IN WHICH A PILOT HOLE OFDESIRED DIAMETER HAS ALREADY BEEN FORMED, A COUNTER TOOL COMPRISING ASHANK PORTION ADAPTED TO BE RECEIVED IN A TOOL HOLDING DEVICE, A CUTTERHEAD SUPPORTED ON THE SHANK PORTION, A PLURALITY OF CUTTING EDGESPROVIDED ON SAID CUTTER HEAD FOR REMOVING MATERIAL IN SAID COUNTERBORINGOF SAID SHEET METALS WORKPIECE, SAID EDGES PROJECTING RADIALLY OF SAIDCUTTER HEAD AND DEFINING THEREBETWEEN A SERIES OF PASSAGES THROUGH WHICHTHE MATERIAL REMOVED BY SAID COUNTERBORING PASSES ALL THE WAY THROUGHTHE CUTTER HEAD, SAID CUTTER HEAD FORMED WITH AN AXIAL RECESS DEFININGTHEREIN A CENTRALLY LOCATED BORE, A PILOT FOR SAID TOOL, THE PILOTHAVING AT ITS REARWARD END A SHANK PORTION, SAID SHANK PORTION REMOVABLYRECEIVED IN SAID BORE WHEREBY SAID PILOT IS INTERCHANGEABLY MOUNTED ONSAID TOOL, SAID BORE AND SHANK PORTION LOCKED AGAINST RELATIVE ROTATION,A CYLINDRICAL GUIDE PORTION FORMED AT THE FORWARD END OF SAID PILOT,SAID FORWARD GUIDE PORTION HAVING A SMOOTH, NON-BORING SURFACE ANDPROPORTIONED FOR A PILOTING FIT IN THE PILOT HOLE ALREADY FORMED IN THESHEET METAL WORKPIECE WHEREBY IT WILL GUIDE AND CENTER SAID TOOL IN SAIDHOLE CONTINUING UNTIL SAID COUNTERBORING IS ALMOST DONE, AND REAMERMEANS FORMED ON THE REARWARD END OF SAID PILOT GUIDE PORTION PROXIMATESAID CUTTER HEAD, SAID REAMER MEANS PRESENTING CUTTING EDGES EXTENDINGOUTWARDLY OF SAID CYLINDRICALLY GUIDE PORTION TO A DIAMETER GREATER THANTHAT OF THE TOOL SHANK PORTION AND EXTENDING OUTWARDLY ALSO OF THEINNERMOST PORTION OF SAID CUTTING EDGES FOR REAMING, FROM THE PROTRUDINGSLUG SECTION FORMED AROUND SAID PILOT GUIDE PORTION UPON THE COMPLETIONOF SAID COUNTERBORING, SMALL PORTIONS OF SAID SLUG SECTION WHICHIMMEDIATELY SURROUND THE PILOT, WHEREBY TO INCREASE THE SIZE OF THEPILOT HOLE IN THE PROTRUDING SLUG SECTION, TO OVERCOME JAMMING ORSTICKING OF THE SLUG SECTION ON THE PILOT, AND TO ENABLE THE SLUGSECTION READILY TO DROP OFF FROM THE PILOT.